Coexistence techniques in wireless networks

ABSTRACT

Techniques are provided for frequency coordination among two different wireless network protocols, such as the IEEE 802.11 and Bluetooth protocols, operating in proximity with one another. Coordination is accomplished by the use of a first radio transceiver operating in accordance with a first communication protocol (which may be the 802.11 protocol) and using a frequency band (which may be the 2.4 GHz band), a base station connected to a wired network and operating in accordance with the first communication protocol, a second radio transceiver operating in accordance with a second communication protocol (which may be the Bluetooth protocol) and using the frequency band, and a coordinator associated with the base station for, in turn, activating the first radio transceiver, deactivating the first radio transceiver, activating the second radio transceiver, and deactivating the second radio transceiver.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/714,803, filed Nov. 16, 2000, now U.S. Pat. No. 7,039,358, issued May2, 2006, which claims the benefit of U.S. Provisional Application Ser.No. 60/175,262, filed Jan. 10, 2000 and U.S. Provisional ApplicationSer. No. 60/196,979, filed Apr. 13, 2000, each of which are incorporatedin their entireties herein, and from which priority is claimed.

BACKGROUND OF THE INVENTION

This invention relates to wireless data communications networks, and inparticular to arrangements for ensuring coexistence between wirelessnetworks that share the same frequency band with different operatingprotocols.

Wireless devices communicate with one another using agreed-uponprotocols that are transmitted in predefined frequency bands. Often,devices using one or more wireless protocols may operate by transmissionwithin the same frequency band. It is therefore necessary to developcoordination techniques in order for devices using one or more wirelessprotocols to efficiently operate in the same band of frequencies at thesame time.

For example, the assignee of the present invention supplies wirelessdata communications systems known as the Spectrum 24® System thatfollows the communications protocol of IEEE 802.11 Standard (802.11),which is hereby incorporated by reference. In the system as implemented,mobile units (MUs) are in data communication with a central computerthrough one or more access points (APs). The APs may communicate with acomputer directly or over an Ethernet wired network. Each of the MUsassociates itself with one of the APs. As defined in 802.11, thiscommunications protocol uses the 2.4 GHz ISM frequency band.

As currently designed, 802.11 devices may use several predefined methodsfor transmission within the 2.4 GHz band to perform as a wireless localarea network. One method is to use a frequency hopping spread spectrum(FHSS) mechanism wherein data is transmitted for a certain period oftime in a particular channel and, following a pseudorandom sequence,continues transmission at a different channel for the same predeterminedlength of time. As currently designed, 802.11 devices operate at afrequency hopping rate of 10 hops/second. Another method is to use adirect sequence spread spectrum (DSSS) mechanism wherein the data istransmitted in a predetermined frequency channel and is multiplied by apseudorandom chipping sequence during transmission.

As all 802.11 devices use the same ISM frequency band, interferenceamong these devices is minimized by use of a Carrier Sense MultipleAccess/Collision Avoidance (CSMA/CA) protocol. Under CSMA/CA, an 8021.11device listens for another's devices transmission prior to initiatingits own transmission. If no other transmission is detected, the devicetransmits its information and waits for an acknowledgment (ACK) from thereceiving device. If no acknowledgment of receipt is received after apre-determined time interval, the device will retransmit after waitingfor a randomly chosen interval of time. Thus, if two or more devicesbegan transmitting coincidentally at the same time and the resultinginterference blocks all of the transmissions, each device will wait arandom amount of time to attempt a retransmission. This allows thedevices to transmit at different times.

Another example of a wireless specification that also uses the 2.4 GHzISM frequency band is Bluetooth™, which is designed for communicationamong devices within a short range transmitting at a lower power level.The Bluetooth specification, version 1.1, which would be known to one ofordinary skill in the art, is fully incorporated herein by reference. Ascurrently designed, Bluetooth operates using a frequency hopping spreadspectrum mechanism at a rate of 1600 hops/second. Bluetooth uses amaster/slave system of communication. One example of a Bluetooth networkmay be a mobile device attached to the user's belt that communicateswith a cordless scanner for reading bar codes and worn by the user as aring. In this case, the mobile device would operate as the master andthe cordless ring scanner would operate as the slave. In this system fordata transmission, the master and slave only communicate at predefinedintervals. At the first interval, the master may communicate to a firstslave device, which may only respond during the second interval. At thethird interval, a master may communicate to a second slave device, whichmay only respond during a fourth interval. By using this system, it isensured that only one device within a particular Bluetooth “piconet” istransmitting at any particular time. Thus, interference is minimized.

Additionally, it is desirable for one Bluetooth piconet to operate inclose proximity with another, separate Bluetooth piconet. Because thereare 79 different frequency channels used by Bluetooth, differentBluetooth networks are unlikely to be operating on the same frequency atthe same time. Interference between the separate Bluetooth piconets isthus minimized. This allows, for example, multiple individuals workingin close proximity with one another to each have his or her own mobileunit along with a cordless ring scanner.

Along with the need to operate multiple networks of the same protocol inclose proximity, there is also a recognized need in the art tocoordinate the transmissions of devices operating under differentprotocols that use the same frequency band. For example, it may bedesirable to use a cordless ring scanner that communicates withbelt-mounted terminal using the Bluetooth protocol while the same beltmounted terminal communicates with an access point using the 802.11protocol. For example, once the user scans-a bar code using the cordlessring scanner, the bar code information may be sent to the belt-mountedterminal. That bar code information may then be transmitted to the802.11 AP. Then an acknowledgment, and possibly a message, may need tobe sent from the AP back to the belt-mounted terminal. The terminal mayalso need to communicate with other Bluetooth enabled peripherals like aprinter or a headset. Although communication protocols such as 802.11and Bluetooth are designed to ensure that devices using the sameprotocol may operate in the same frequency band with a minimum ofinterference, there has heretofore been no method of coordination forthe use of these wireless devices in the same frequency operating underdifferent communication protocols.

It is additionally desirable to provide voice service using theBluetooth communications protocol, for example, between a belt-mountedterminal and a headset worn by the user. Bluetooth supports voicecommunications using Synchronous Connection Oriented (SCO) voice packetswhich are transmitted every 3.75 ms. The requirement for such frequentBluetooth packet transmission makes it difficult to coordinate voicetransmission using the Bluetooth SCO packets with 802.11 communications.

It is therefore an object of this invention to utilize coordinationtechniques to ensure that, for example, both Bluetooth and 802.11enabled devices, may operate robustly in the same frequency band at thesame time.

SUMMARY OF THE INVENTION

An embodiment of the present invention includes a first radiotransceiver operating in accordance with a first communication protocol(which may be the 802.11 protocol) and using a frequency band (which maybe the 2.4 GHz ISM band), a base station operating in accordance withthe first communication protocol, a second radio transceiver operatingin accordance with a second communication protocol (which may be theBluetooth protocol) and using the frequency band, and a coordinatorassociated with the base station for, in turn, activating the firstradio transceiver, deactivating the first radio transceiver, activatingthe second radio transceiver, and deactivating the second radiotransceiver.

The first radio transceiver and the second radio transceiver may bemounted together in a housing, which may be suitable for wearing on abelt or a laptop computer or a PDA. One or more slave devices may beassociated with the second transceiver and operate in accordance withthe second communication protocol. The slave devices may include ascanner, worn on a user's finger and capable of transmitting bar codeinformation to the second transceiver, a printer, or a personal datamanaging device.

In one arrangement wherein the first and second transceivers are mountedtogether in a housing, they may include orthogonally polarized antennas.In another arrangement a Bluetooth protocol transceiver transmits atpower level of about 0 dBm. In still another arrangement, two or moresub bands within the frequency band are provided and the 802.11 protocoltransceiver uses one of the two or more sub-bands and the Bluetoothprotocol transceiver uses another of the two or more sub-bands. In stillanother arrangement in the second radio transceiver is equipped with alook-ahead function for determining whether two or more sub-bands arebeing used by the first radio transceiver that will also be used by thesecond transceiver. In still another arrangement, a coordinator isassociated with the first radio transceiver for deactivating the secondradio transceiver while the first radio transceiver is in use.

According to the invention, there is provided a method for operating aportable data communications device using first and second wireless datacommunications protocol. The data communications device is operated in apower saving mode of the first communication protocol, whereby thedevice has active time periods for transmitting and receiving datacommunications signals using the first communications protocol anddormant time periods during which the device neither transmits norreceives data communications signals using the first protocol. The datacommunications device is operated as a master device according to thesecond communications protocol whereby the data communication devicecontrols operation of slave devices communicating therewith. Theoperation according to the second data communications protocol iscontrolled to operate only during the dormant time periods of the firstprotocols.

In one embodiment, a signal indicating that the active time period willcommence following a predetermined time interval is provided toterminate operation according to the second data communication protocolduring the predetermined time interval. The first wireless datacommunications protocol may be the 802.11 protocol. The second wirelesscommunication protocol may be Bluetooth.

In another aspect of the invention, there is provided a method foroperating a wireless data communications system having an access pointand at least one mobile unit associated with said access point using afirst wireless protocol (which may be 802.11), wherein said mobile unitis arranged to conduct wireless data communications with other unitsusing a second wireless protocol (which may be Bluetooth). Periodicbeacon signals are transmitted from the access point according to thefirst wireless protocol. Global clear to send signals are transmittedfrom the access point according to the first wireless protocol, wherebythe global clear to send signals prevent mobile units from transmittingsignals using the first data communications protocol during an allocatedtime interval within the beacon signal period. The access point iscontrolled to avoid transmissions during the allocated time interval,and the mobile unit is operated in response to the global clear to sendsignal to conduct wireless communications acting as a master unit usingthe second wireless protocol during the allocated time interval.

In one embodiment, the beacon signal period is divided into three timeintervals, wherein the access point conducts power saving mode datacommunications during a first time interval, wherein the access pointconducts data communications using the second communications protocolduring the second time interval and wherein the access point conductsdata communications using the first wireless protocol during a thirdtime interval. The first time interval may immediately following thebeacon signal. In another embodiment, the first time interval may not beutilized.

In accordance with another aspect of the invention, there is provided amethod of operating a data communications system using a master-slaveprotocol (such a Bluetooth), wherein a master transceiver transmits toslave units during first even time slots and wherein slave unitstransmit to the master unit during odd time slots, and wherein thetransmissions follow a predetermined frequency hop pattern at a hop ratecorresponding to the time slots. The master unit is operated during afirst time period of each time slot to detect interfering signals at afrequency corresponding to the following time slot. Transmission by themaster transceiver is inhibited during even time slots if interferingsignals have been detected during either of the current or previous timeslots.

In a preferred practice, the operating step includes tuning the masterunit to receive signals corresponding to the frequency allocated to thenext following time slot; detecting the strength of signals received andretuning the master unit to send or receive signals corresponding to thefrequency allocated to the current time slot.

In another aspect of the invention, there is provided a method forproviding voice communications in a wireless data communications systemhaving a mobile unit arranged to communicate with an access point usinga first data communications protocol (such as 802.11) and arranged tocommunicate with other devices using a second data communicationsprotocol (such as Bluetooth). Data corresponding to the voicecommunication is communicated between the access point and the mobileunit using the first data communications protocol. The datacorresponding to the voice communications is communicated between themobile unit and a portable device using the second data communicationprotocol. The communication is arranged at time intervals which avoidinterference with the communicating using the first data communicationsprotocol. Voice signals are converted to data corresponding to the voicesignals and data signals corresponding to voice signal are convertedinto voice signals in the portable device.

In a preferred arrangement, the data corresponding to voice signalscomprises compressed voice signal data. The communication between themobile unit and the portable device preferably uses a Bluetooth ACLlink.

According to a further aspect of the invention, there is provided amethod for operating a mobile unit arranged to communicate using firstand second data communication protocols operating in the same frequencyband (such as 802.11 and Bluetooth) wherein the mobile unit associateswith an access point and receives therefrom beacon signals demarcatingtime intervals according to the first communications protocol. Signalsare received from the access point (such as CTS signals) designating aportion of one of the time intervals during which mobile unitsassociated with the access point refrain from transmissions using saidfirst data communications protocol. The mobile unit is operated as amaster unit using the second data communications protocol to communicatewith slave units during the designated portion of the time interval.

According to a further aspect of the invention, there is provided amethod for operating a wireless data communications network having atleast one access point and at least one mobile unit, including a mobileunit arranged to communicate with the access point using a firstwireless data communication protocol (such as 802.11) in a firstfrequency band and to communicate with other devices using a secondwireless data communication protocol (such as Bluetooth) in the firstfrequency band. Signals (such as CTS) as sent from the access point inthe first communications protocol, which designate a time period whereinmobile units associated with the access point refrain from transmittingusing the first data communications protocol. The mobile units operateas a master unit to conduct wireless data communications with the otherdevices operating as slave units using the second data communicationsprotocol during the designated time period.

According to still another aspect of the invention, a method is providedfor operating a mobile unit arranged to communicate using first andsecond data communications protocols operating in the same frequencyband (such as 802.11 and Bluetooth), wherein the mobile unit associateswith an access point. The mobile unit receives first and second controlsignals using the first data communications protocol. The mobile unitsare operated in response to the first control signals to act as a masterunit and conduct data communications with slave units using the seconddata communications protocol. Communications by the mobile unit usingthe second data communications protocol is discontinued in response tothe second control signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communications system using802.11 and Bluetooth devices.

FIG. 2 is a block diagram of a wireless communications system using802.11 and Bluetooth devices at the same time along with a connectbutton switch and connected indicators.

FIG. 3 is a schematic diagram of an embodiment of the present inventionillustrating a coordinated time line between the operation of 802.11 andBluetooth devices.

FIG. 4 is a schematic diagram of an embodiment of the present inventionillustrating another coordinated time line between the operation of802.11 and Bluetooth devices.

FIG. 5 is a diagram showing a modified Bluetooth operating method foravoiding interference.

FIG. 6 is a drawing showing one example of orthogonally polarizedantennas.

FIG. 7 is a drawing of a wireless headset arranged for voicecommunications.

FIG. 8 is a block diagram of the headset of FIG. 7.

DESCRIPTION OF THE INVENTION

Turning to FIG. 1, shown are a plurality of base stations or AccessPoints (APs) 20, 30 that are physically connected 40, 50 to a wirednetwork 10. While a wired network with multiple access points connectedto a CPU 12 is a typical installation, the system may use a singlecomputer and single AP. Each AP contains apparatus 60, 70 for thetransmission and reception of radio frequency (RF) signals under the802.11 protocol. Also using the 802.11 protocol, a plurality of radiotransceivers or mobile units (MUs) 120, 140 communicate using apparatus80, 90 for the transmission and reception of RF signals. Each MU 120,140 may also be associated with a radio transceiver which is a BluetoothMaster (BTM) device 130, 150, which together make up a dual mode devices100, 110. The association between the MU and BTM may be, for example, byway of being physically housed in the same unit. An example of a dualmode device 100, 110 may be portable terminal worn on a belt.

Each BTM 130, 150 communicates with one or more Bluetooth Slave (BTS)devices 160, 170, 180, 190, 200, 210 via the Bluetooth protocol. TheBluetooth protocol is established such that each BTS is uniquelyassociated with a BTM. Thus, as illustrated, BTSIA 160, BTS1B 170, andBTS1C 180 communicate using RF signals 220, 230, 240 only with BTMI 130.This forms a piconet 280. Correspondingly, BTS2A 190, BTS2B 200, andBTS2C 210 communicate using RF signals 250, 260, 270 with BTM2 150. Thisforms a piconet 290. An example of a BTS may be a cordless ring scanner,a printer, or personal data managing device.

With no coordination, there will be times when the BTM 130, 150 and theassociated MU 120, 140 attempt to operate at the exact same time. Sincethe two devices operate in the same 2.4 GHz ISM frequency band the BTM130, 150 and the MU 120, 140 may severely interfere with one another,especially if they are housed in a dual mode device 100, 110. Therefore,there is a need for coordination between the two devices. One suchcoordination scheme is primarily based on time multiplexing of the802.11 and BT radios, which is especially suitable for a controlledenvironment (e.g., the 802.11 and BT radios are housed in the sameterminal or dual mode device). In one embodiment, the Bluetooth systemsare enabled or disabled according to a global/central signal from the802.11 AP as described herein. The central signal may also becoordinated among the two devices without coordinating with the AP.

In a further embodiment, the dual mode devices 100, 110 may be designedsuch that the 802.11 antennas 80, 90 have orthogonal polarization withrespect to the Bluetooth antennas used to generate RF signals 220, 230,240, 250, 260, 270. This technique may provide additional protectionfrom 802.11 Bluetooth interference and does not require the need forcentralized control.

FIG. 6 shows one example of orthogonally polarized antennas that can beused to reduce interference. The antenna structure of FIG. 6 includes avertically polarized monopole antenna 502, which is connected to atransmitter/receiver by an unbalanced transmission line 510. Thestructure also includes a horizontally polarized dipole antenna havingdipole arms 504, 506 which are connected to a transmitter/receiver bybalanced transmission line 508. Those skilled in the art will recognizethat many other orthogonal-polarized antenna configurations may be used.

In a further embodiment, the BTMs 130, 150 may be designed to transmitat a relatively low power level such as lower than 0 dBm. This techniquemay provide additional protection from 802.11 Bluetooth interference andmay be used with other antenna or frequency coordination methodsdiscussed herein.

In a further embodiment, the 802.11 APs 20, 30 and MUs 120, 140 may bedesigned to operate in one portion of the 2.4 GHz spectrum, while theBTMs 130, 150 and BTSs 160, 170, 180, 190, 200, 210 may be designed tooperate in another portion of the 2.4 GHz spectrum.

In a further embodiment, the BTMs 130, 150 may be equipped with alook-ahead function to determine which frequencies within the 2.4 GHzband will be used for two or more future Bluetooth frequency hops tooccur. If the BTM 130, 150 determines that one of the next two or morefrequency hops will use the same frequency that the 802.11 system isusing, the BTMs 130, 150 will blank their output, thus reducing theeffect of the interference on the 802.11 transmissions. By using thismethod, interference between Bluetooth and 802.11 could be reduced oreliminated at the expense of dropping a couple of packets when channeloverlap occurs. This approach may also be expanded to include theblanking of adjacent channels that may also interfere with the 802.11transmissions.

Bluetooth uses a Frequency Hopping Spread Spectrum (FHSS) radio, whichhops much faster than most IEEE 802.11 radios. Bluetooth sends a shortpacket as it dwells on a given frequency. Most IEEE 802.11 radios hopmuch slower and send much longer packets. Also there are versions ofIEEE 802.11 WLANs that use Direct Sequence Spread Spectrum (DSSS) whichdo not hop and occupy a wide band.

As a result, during the transmission of an IEEE 802.11 packet theBluetooth radio hops across many frequencies and potentially sends apacket on each frequency. These Bluetooth packets can interfere with theIEEE 802.11 packets and cause the IEEE 802.11 packet to be in error. TheIEEE 802.11 packet needs to be retransmitted, and once again may bedestroyed by the signal from the Bluetooth radio.

This technique shown in FIG. 5 can be used in any Bluetooth radio and inany device that will operate in an IEEE 802.11 WLAN environment. Sinceit detects devices radiating in the 2.4 GHz ISM band it could also beused to prevent interference with other devices in that band.

A Bluetooth network consists of up to eight Bluetooth devices operatingin a piconet. The piconet has one master and up to seven slaves. All theBluetooth devices in the piconet hop in unison, at a rate of 1600hops/second. The time that the frequency hopper dwells on a givenfrequency is called the slot time. At this hop rate the slot time is 625microseconds. Typically packets are completed within one slot time,however, it is also possible to have 3 and 5 slot packets. The masterand the slaves take turns transmitting, with the master transmitting oneven slots and the slaves transmitting on odd slots. See also BluetoothSpecification, version 1.0, Dec. 1, 1999, which is hereby incorporatedby reference in full.

There are two types of links between the master and each of the slavedevices in a Bluetooth piconet. There is an asynchronous connection-lesslink (ACL) which is used to transfer data. There is also a synchronousconnection oriented link (SCO) that is used to transfer voice data. Themaster in the picolink determines when data on an ACL link istransferred. Data is transferred when the master has data to send to aslave or the master wants to receive data from a slave.

Each Bluetooth device within a piconet frequency hops in unison,according to a pseudo random sequence. FIG. 5 illustrates a devicehopping along its sequence of frequencies: f(1), f(2), . . . f(n) . . .The figure also shows how the 625-microsecond slot time includes a220-microsecond period for tuning the frequency synthesizer in the radioto a new frequency and a 405-microsecond data transmission period.

As stated above during even slots T(f) the master transmits to a slaveand during odd slots R(f) the slave transmits back to the master. Themaster can transmit on any even time slot. The slave can only transmitto the master in a time slot if the master sent the slave a packet inthe previous time slot. If the master does not send data to any slave inslot n then no slave can transmit in slot (n+1). The exception to thisrule is for SCO link packets in which data is always transmitted inpredefined periodic intervals. So for ACL links if the master does nottransmit any data, the slaves do not send any data.

Currently the piconet master does not attempt to determine if any otherdevices are using the spectrum before it transmits. As a result, ifthere is an IEEE 802.11 packet currently being transmitted the Bluetoothmaster will not bother to check to see if this other system istransmitting and will itself transmit at the same time, and possibly onthe same frequency. As a result it will interfere with the IEEE 802.11packet possibly causing the packet to be received incorrectly.

It is proposed to subdivide the 220 microsecond tuning time intervalinto several subintervals and to spend some of that time looking aheadinto subsequent frequencies to see if there is any other devicestransmitting in those channels. The reason to look ahead is that if thea master sends a message to slave #1 on frequency f(n), then the masterhas cleared slave #1 to transmit during the next time slot on frequencyf(n+1). Therefore, the master needs to look ahead to the frequency thatcorresponds to the next slot. The 220 microsecond timing interval can besubdivided as follows. In the first 80 microseconds the frequencysynthesizer in the master retunes to f(n+1), then in the next 60microseconds the master listens for any signal in that band. This can bedone using a standard Receive Strength Signal Indicator (RSSI) in theradio. Then in the next 80 microseconds the frequency synthesizer thenretunes the radio to f(n). FIG. 5 illustrates the new proposed time slotsubdivision.

Just prior to receiving on frequency f(n−1) the master checks to seethat the frequency band at f(n) is clear. Also, prior to transmitting onfrequency f(n) the master also makes sure that the frequency band f(n)is clear. If frequency bands f(n) and f(n+1) are clear then the masterwill transmit on frequency band f(n) and as a result allow the slave totransmit on frequency band f(n+1), in the next time slot.

During a time slot R the master likewise checks the frequency band thatit will use to transmit in the following time interval. If that timeslot is occupied, it will not transmit.

Referring now to the schematic of FIG. 3 in conjunction with thephysical layout shown in FIG. 1. There is shown another technique tocoordinate transmissions. Every 802.11 beacon time period, T 300, may bedivided into three time intervals: 802.11 communications in the powersaving (PSP) mode—t_(802.11PSP) 310, Bluetooth communications—t_(NAV)320, and 802.11 communications in the active mode CAM—t_(802.11CAM) 330.The duration of time intervals T, t_(802.11IPSP), t_(NAV), andt_(802.11CAM) depend on traffic characteristics and application needs(e.g., time critical services). At the beginning of each beacon period300, AP 20 sends a beacon signal 350 to the 802.11 PSP MU's 120, 140that wake up in this period (some PSP MU's may wake up in a differentbeacon). During this period the PSP MU's 120, 140 receive and transmittheir packets according to the 802.11 protocol. Once all the PSP MU's120, 140 receive their packets, the AP 20, may optionally send a globalClear to Send (CTS) signal 430 to shut down all the 802.11communications for a NAV (Network Allocation Vector) period. At thispoint the 802.11 MUs 120, 140 will enable their associated BTMs 130, 150(which may be housed in the same dual mode devices 100, 110) so thepiconets 280, 290 associated with these BTMs 130, 150 may begin BTcommunications 360, 370. After completion of the NAV period 320 the BTM130, 150 radios are disabled and all BT communications is ceased. Therest of the time (until the next beacon 380) is dedicated for 802.11Continuously Aware Mode (CAM) MU's (not shown) that operate according tothe 802.11 protocol.

In a further embodiment, the t_(802.11PSP) 310 time interval may beeliminated if the MUs do not operate in PSP mode. Here, the CTS signal340 would trigger only t_(NAV) 320 and t_(802.11CAM) 330 time intervalsfor every 802.11 beacon period, T 300.

In a further embodiment, the t_(802.11) CAM 330 time interval may beeliminated if the MUs do not operate in CAM mode. Here, the CTS signal340 would trigger only t_(NAV) 320 and t_(802.11PSP) 310 time intervalsfor every 802.11 beacon period, T 300.

In a further embodiment, the Bluetooth systems are enabled or disabledaccording to a global/central signal from the dual mode devices 100, 110instead of from an AP 20.

A further embodiment of the present invention may be demonstrated byreferring to the schematic of FIG. 4 in conjunction with the physicallayout shown in FIG. 1. In this approach there is no need for the 802.11APs to coordinate between Bluetooth and 802.11 transmission. Instead,the Bluetooth network operates in the ordinary course until a 802.11 MUinstructs one or all of the Bluetooth masters to stop transmittingmessages to the Bluetooth slaves. When using Asynchronous Connectionless(ACS) packets, the Bluetooth master controls access to the medium forits piconet. Thus, if the masters stops transmitting the slaves stop aswell. Once the 802.11 MU has completed its communication, the Bluetoothmasters are allowed to resume communicating with the Bluetooth slaves.This technique is especially useful when all the 802.11 MUs are in PSPmode, because these devices are in suspended mode during most of thetime.

As shown in FIG. 4, when the MU 120 desires to initiate 802.11communication, its sends a STOP signal 400 to the BTMs 130, 150. The MU120 then communicates 450 using the 802.11 protocol with the AP 20. Whenthe MU 120 is finished communicating for the period t_(802.11) 470 andis ready to resume its power save mode, the MU 120 communicates a STARTsignal 410 to the BTMs 130, 150. The BTMs 130, 150 may then proceed tocommunicate 430, 440 using the BT protocol with their respective BTSs160, 170, 190, 200 during the period tBT 480. When the MU 120 802.11terminal “wakes up” to either send data or to listen for a 802.11 beaconfrom the AP 20, the MU 120 sends a STOP signal 420 to the BTMs 130, 150to inform then that the MU 120 is taking over access to the medium. TheMU 120 may warn the BTMs 130, 150 before it needs exclusive use of themedium, and this warning may occur, for example, about 4 [sec beforeaccess is required. This allows the BTMs 130, 150 to complete severalpacket transfers and then stop communicating with their respective BTSs160, 170, 190, 200. Subsequently the MU 120 may communicate 460 with theAP 20 for a new period t_(802.11) 490.

In a further embodiment, the periods t_(802.11) 490 and t_(BT) 480 areat fixed, predetermined intervals throughout the communications process.In a further embodiment, the periods t_(802.11) 490 and t_(BT) 480 areequal length of time.

In a further embodiment, a BTS 160, 170, 180, 190, 200, 210 may be, forexample, a headset or voice transmission device designed to transmitvoice data to the BTMs 110, 130, which is then transmitted via the802.11 network. Voice information is normally transmitted on a Bluetoothnetwork using the periodic Synchronous Connection Oriented (SCO)protocol. This protocol is not conducive to the transmissioninterruptions required to coordinate with 802.11 operation. It would bemore efficient, when using Bluetooth and 802.11, to transmit voice overthe Bluetooth network using the ACL protocol that is normally reservedfor data transmission. To use voice transmission over Bluetooth, whenused in conjunction with the frequency coordination techniques disclosedherein, the Bluetooth piconet 280, 290 needs to compress and decompressthe voice information in order to use the ACL protocol normally reservedfor data transmissions.

Referring to FIGS. 7 and 8, there is shown a voice communication system520 including a headset 521 having a BTS radio unit 210 whichcommunicates with a dual mode mobile unit 110 using the BT protocol. Theheadset 521 includes an earphone in the same housing as radio unit 210and a microphone 522. Mobile unit 110 may be arranged to be worn on thebelt of a user. As shown in FIG. 8, BTS 210 include microphone 522,earphone 524, and D to A and A to D converter 526 for converting soundsignals to digital signals and vice versa. Digitized sound signals arecompressed and arranged in packets in processor 528 and transmittedusing RF module 530 and antenna 532. The reverse process is used forreceived signals. RF module 530 communicates with MU 110 using BTprotocol in the ACL mode.

Another issue that results from attempts to coordinate 802.11 andBluetooth devices is ensuring that the lower power Bluetooth devices areactually operating in conjunction with the higher power 802.11 devices.In this regard, a further embodiment of the present invention may bedemonstrated by referring to FIG. 2. FIG. 2 is substantially similar toa portion of FIG. 1, with the addition of a connect button 500 thatprovided on MUs 140 of the 802.11 network and light 540. The connectbutton 500, may be physically mounted on a dual mode device 110. Whenactivated by the user, the connect button 500 instructs the mobile units140 to stop transmitting (timeout) for a preset amount of time. Forexample, the timeout could last for 10 seconds. This timeout would allowthe Bluetooth piconet 290 to establish operations free from interferencefrom 802.11 devices for the timeout period. Once established, thepiconet 290 may activate light 540 to assure the user that the Bluetoothpiconet 290 has in fact, been established. Once the timeout period ends,other methods for frequency coordination as described herein may beutilized.

While there have been described what are believed to be the preferredembodiments of the present invention, those skilled in the art willrecognize that other changes and modifications may be made theretowithout departing from the spirit of the present invention, and it isintended to claim all such changes and modifications as fall within thetrue scope of the invention.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 11.(canceled)
 12. (canceled)
 13. (canceled)
 14. (canceled)
 15. (canceled)16. (canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled) 20.(canceled)
 21. (canceled)
 22. (canceled)
 23. (canceled)
 24. (canceled)25. (canceled)
 26. (canceled)
 27. (canceled)
 28. (canceled)
 29. A methodfor operating a wireless data communications system having an accesspoint and at least one mobile unit associated with said access pointusing a first wireless protocol, wherein said mobile unit is arranged toconduct wireless data communications with other units using a secondwireless protocol, comprising: transmitting periodic beacon signals fromsaid access point according to said first wireless protocol;transmitting global clear to send signals from said access pointaccording to said first wireless protocol, said global clear to sendsignals preventing mobile units from transmitting signals using saidfirst data communications protocol during an allocated time intervalwithin said beacon signal period; controlling said access point to avoidtransmissions during said allocated time interval; operating said mobileunit in response to said global clear to send signal to conduct wirelesscommunications acting as a master unit using said second wirelessprotocol during said allocated time interval.
 30. A method as specifiedin claim 29 wherein said first wireless data communications protocol isthe IEEE 802.11 protocol.
 31. A method as specified in claim 30 whereinsaid second wireless communication protocol is Bluetooth.
 32. A methodaccording to claim 29 wherein said beacon signal period is divided intothree time intervals, and wherein said access point conducts powersaving mode data communications during a first time interval, whereinsaid allocated time interval is a second time interval and wherein saidaccess point conducts data communications using said first wirelessprotocol during a third time interval.
 33. A method according to claim32 wherein said first time interval is immediately following said beaconsignal.
 34. A method as specified in claim 32 wherein said firstwireless data communications protocol is the IEEE 802.11 protocol.
 35. Amethod as specified in claim 34 wherein said second wirelesscommunication protocol is Bluetooth.
 36. A method of operating a datacommunications system using a master-slave protocol, wherein a mastertransceiver transmits to slave units during first even time slots andwherein slave units transmit to said master unit during odd time slots,and wherein said transmissions follow a predetermined frequency hoppattern at a hop rate corresponding to said time slots, comprising:operating said master unit during a first time period of each time slotto detect interfering signals at a frequency corresponding to thefollowing time slot, and inhibiting transmission by said mastertransceiver during even time slots if interfering signals have beendetected during either of the current or previous time slots.
 37. Amethod according to claim 36, wherein said operating step comprisestuning said master unit to receive signals corresponding to thefrequency allocated to the next following time slot; detecting thestrength of signals received and retuning said master unit to send orreceive signals corresponding to the frequency allocated to the currenttime slot.
 38. A method according to claim 37 wherein said protocol isBluetooth.
 39. (canceled)
 40. (canceled)
 41. (canceled)
 42. (canceled)43. (canceled)
 44. (canceled)
 45. A method for operating a mobile unitarranged to communicate using first and second data communicationprotocols operating in the same frequency band wherein said mobile unitassociates with an access point and receives therefrom beacon signalsdemarcating time intervals according to said first communicationsprotocol, comprising: receiving signals from said access pointdesignating a portion of one of said time intervals during which mobileunits associated with said access point refrain from transmissions usingsaid first data communications protocol, and operating said mobile unitas a master unit using said second data communications protocol tocommunicate with slave units during said designated portion of said timeinterval.
 46. A method as specified in claim 45 wherein said firstprotocol is the IEEE 802.11 protocol.
 47. A method as specified in claim46 wherein said signals comprise CTS signals.
 48. A method as specifiedin claim 47 wherein said second protocol is Bluetooth.
 49. A method foroperating a wireless data communications network having at least oneaccess point and at least one mobile unit, including a mobile unitarranged to communicate with said access point using a first wirelessdata communication protocol in a first frequency band and to communicatewith other devices using a second wireless data communication protocolin said first frequency band, comprising: transmitting signals from saidaccess point in said first communications protocol, said signalsdesignating a time period wherein mobile units associated with saidaccess point refrain from transmitting using said first datacommunications protocol; and operating said mobile units as a masterunit to conduct wireless data communications with said other devicesoperating as slave units using said second data communications protocolduring said designated time period.
 50. A method as specified in claim49 wherein said first communications protocol is the IEEE 802.11protocol.
 51. A method as specified in claim 49 wherein said signalscomprise CTS signals.
 52. A method for operating a mobile unit arrangedto communicate using first and second data communications protocolsoperating in the same frequency band, wherein said mobile unitassociates with an access point, comprising: receiving in said mobileunit first and second control signals using said first datacommunications protocol; operating said mobile unit in response to saidfirst control signals to act as a master unit and conduct datacommunications with slave units using said second data communicationsprotocol; and discontinuing communications by said mobile unit usingsaid second data communications protocol in response to said secondcontrol signal.
 53. (canceled)
 54. (canceled)